of/gpio: stop using device_node data pointer to find gpio_chip

Currently the kernel uses the struct device_node.data pointer to resolve
a struct gpio_chip pointer from a device tree node.  However, the .data
member doesn't provide any type checking and there aren't any rules
enforced on what it should be used for.  There's no guarantee that the
data stored in it actually points to an gpio_chip pointer.

Instead of relying on the .data pointer, this patch modifies the code
to add a lookup function which scans through the registered gpio_chips
and returns the gpio_chip that has a pointer to the specified
device_node.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Anton Vorontsov <avorontsov@ru.mvista.com>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: David Brownell <dbrownell@users.sourceforge.net>
CC: Bill Gatliff <bgat@billgatliff.com>
CC: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Jean Delvare <khali@linux-fr.org>
CC: linux-kernel@vger.kernel.org
CC: devicetree-discuss@lists.ozlabs.org

2 files changed, 6 insertions, 0 deletions

diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
index af2544ef0b59..c7376bf80b06 100644
--- a/include/asm-generic/gpio.h
+++ b/include/asm-generic/gpio.h
@@ -127,6 +127,9 @@ extern int __must_check gpiochip_reserve(int start, int ngpio);
 /* add/remove chips */
 extern int gpiochip_add(struct gpio_chip *chip);
 extern int __must_check gpiochip_remove(struct gpio_chip *chip);
+extern struct gpio_chip *gpiochip_find(void *data,
+                                        int (*match)(struct gpio_chip *chip,
+                                                     void *data));
 
 
 /* Always use the library code for GPIO management calls,
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index 460d6810c5eb..1020587efed1 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -54,6 +54,9 @@ extern int of_mm_gpiochip_add(struct device_node *np,
                               struct of_mm_gpio_chip *mm_gc);
 extern int of_gpio_simple_xlate(struct gpio_chip *gc, struct device_node *np,
                                 const void *gpio_spec, u32 *flags);
+
+extern struct gpio_chip *of_node_to_gpiochip(struct device_node *np);
+
 #else /* CONFIG_OF_GPIO */
 
 /* Drivers may not strictly depend on the GPIO support, so let them link. */